The next logical step is to slash the thousands of American and Russian tactical or "battlefield" nuclear weapons, which are meant to support troops in the field during a conflict.

Today, these weapons serve no military purpose. During the Cold War, the United States deployed them in Europe to deter a Soviet attack against our NATO allies, but a Russian invasion through the Fulda Gap is no longer a major concern. America's strategic nuclear arsenal and conventional military superiority provide all the deterrence NATO needs. While strategic nuclear weapons will be necessary to protect the United States for many years, tactical nuclear weapons are a dangerous and unnecessary expense for everyone, and especially for Moscow.

Russia has thousands more tactical nuclear weapons than we do, and our allies sometimes consider U.S. deployment of such weapons in Europe to be concrete proof of our commitment to NATO's defense. So it will not be easy for the United States to negotiate a deal reducing or, better still, eliminating them. Yet, in an age when every tactical nuclear weapon the world gets rid of is one less that could fall into the hands of terrorists or a rogue state, these political challenges seem well worth tackling.

John Nagl is the president of the Center for a New American Security and the author of "Learning to Eat Soup With a Knife: Counterinsurgency Lessons From Malaya and Vietnam." He can be reached at john.nagl@gmail.com.